Container and composition for enhanced gas barrier properties

ABSTRACT

A container comprising a polyester composition with enhanced carbon dioxide and oxygen barrier properties and methods of improving the gas barrier properties of polyester containers are provided. The polyester composition comprises a polyester and a gas barrier enhancing additive. In a particular embodiment, the gas barrier enhancing additive comprises a compound having the chemical formula:
 
X—(X 1 ) s —COO—(X 2 ) t —X 3 —(X 4 ) u —OOC—(X 5 ) v —X 6  
 
or
 
X—(X 1 ) s —OOC—(X 2 ) t —X 3 —(X 4 ) u —COO—(X 5 ) v —X 6 .

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.14/228,932, filed Mar. 28, 2014, now U.S. Pat. No. 9,051,116, which is acontinuation of U.S. application Ser. No. 12/629,379, filed Dec. 2,2009, now asbandoned, which claims benefit of U.S. ProvisionalApplication No. 61/121,036, filed Dec. 9, 2008, each of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to a packaged beverage, and more particularly toenhancing the carbon dioxide and oxygen barrier properties of acontainer for a packaged beverage, thereby increasing the shelf life ofits contents, by incorporating an additive into polyethyleneterephthalate (PET) and its copolyesters.

BACKGROUND

Polyethylene terephthalate and its copolyesters (hereinafter referred tocollectively as “PET”) are widely used to make containers for carbonatedsoft drinks, juice, water, and the like due to their excellentcombination of clarity, mechanical, and gas barrier properties. In spiteof these desirable characteristics, oxygen and carbon dioxide gasbarrier properties of PET limit application of PET for smaller sizedpackages, as well as for packaging oxygen sensitive products, such asbeer, juice, and tea products. A widely expressed need exists in thepackaging industry to further improve the gas barrier properties of PET.

The relatively high permeability of PET to carbon dioxide limits the useof smaller PET containers for packaging carbonated soft drinks. Thepermeation rate of carbon dioxide through PET containers is in the rangeof 3 to 14 cc's per day or 1.5 to 2 percent per week loss rate at roomtemperature depending on the size of the container. A smaller containerhas a larger surface area to volume ratio resulting in a higher relativeloss rate. For this reason, PET containers are currently used only aslarger containers for packaging carbonated soft drinks, while metal cansand glass containers are the choice for smaller carbonated soft drinkcontainers.

The amount of carbon dioxide remaining in a packaged carbonated softdrink determines its shelf life. Normally, carbonated soft drinkcontainers are filled with approximately four volumes of carbon dioxideper volume of water. It is generally accepted that a packaged carbonatedsoft drink reaches the end of its shelf life when 17.5 percent of thecarbon dioxide in the container is lost due to permeation of the carbondioxide through the container side wall and closure. The permeability ofPET to carbon dioxide therefore determines the shelf life of thepackaged carbonated beverage and thus, the suitability of PET as apackaging material.

Numerous technologies have been developed or are being developed toenhance the barrier of PET to small gas molecules, but some are tooexpensive and others may cause undesirable change in PET mechanicalproperties, stretch ratio, and/or clarity.

Thus, there is a need in the art to enhance the barrier performance ofPET for use in applications that will require enhanced barrier, such asin the packaging of carbonated beverages and oxygen sensitive beveragesand foods, in a manner that does not cause substantial degradation ofthe PET mechanical properties, does not substantially impact the stretchratio of the PET, and/or does not negatively impact the clarity of thePET.

SUMMARY

The embodiments provided herein address the above-described needs byproviding a polyester container with enhanced gas barrier properties.The polyester container comprises a polyester composition comprised of apolyester and a gas barrier enhancing additive. In an embodiment, thegas barrier enhancing additive comprises a compound having the chemicalstructure of Formula I or Formula II:

wherein X and X⁶, independent of one another, comprise hydrogen, halide,heteroatom, hydroxyl, amino, amido, alkylamino, arylamino, alkoxy,aryloxy, nitro, acyl, cyano, sulfo, sulfato, mercapto, imino, sulfonyl,sulfenyl, sulfinyl, sulfamoyl, phosphonyl, phosphinyl, phosphoryl,phosphino, thioester, thioether, anhydride, oximno, hydrazino, carbamyl,phosphonic acid, phosphonato, or a C₁-C₁₀ monovalent hydrocarbon whichmay be unsubstituted or substituted with one or more functionalmoieties;

wherein X¹, X², X³, X⁴, and X⁵, independent of one another, comprise aheteroatom or a C₁-C₁₀ divalent hydrocarbon, wherein each heteroatom orC₁-C₁₀ divalent hydrocarbon may be unsubstituted or substituted with oneor more functional moieties or one or more C₁-C₁₀ hydrocarbyls that maybe unsubstituted or substituted with one or more functional moieties;and

wherein s, t, u, and v, independent of one another, may be a number from0 to 10;

wherein when X³ comprises a C₆ or C₁₀ divalent aromatic hydrocarbon, Xand X⁶, independent of one another, comprise a hydrogen, halide,heteroatom, hydroxyl, amino, amido, alkylamino, arylamino, alkoxy,aryloxy, nitro, acyl, cyano, sulfo, sulfato, mercapto, imino, sulfonyl,sulfenyl, sulfinyl, sulfamoyl, phosphonyl, phosphinyl, phosphoryl,phosphino, thioester, thioether, anhydride, oximno, hydrazino, carbamyl,phosphonic acid, phosphonato, or a C₃-C₁₀ monovalent cyclic orheterocyclic non-aryl hydrocarbon which may be unsubstituted orsubstituted with one or more functional moieties.

According to another embodiment, a method for enhancing gas barrierproperties of a polyester container is provided, the method comprisingblending a polyester with such a gas barrier enhancing additive to forma polyester composition. According to particular embodiments, thepolyester composition can be formed into articles such as a container.

Furthermore, in another embodiment, the step of forming the containercomprises stretch blow molding. Particular embodiments provide polyestercontainers, such as PET containers, with enhanced gas barrier, and inparticular, enhanced gas barrier to carbon dioxide and oxygen. Thismakes certain embodiments particularly suited for packaging carbonatedsoft drinks and oxygen sensitive beverages and foods. Particularembodiments may achieve this enhanced gas barrier while maintainingacceptable physical properties and clarity.

Other objects, features, and advantages of this invention will becomeapparent from the following detailed description, drawings, and claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a system for making a PET containerwith enhanced gas barrier in accordance with an embodiment.

FIG. 2 is a sectional elevation view of a molded container preform madein accordance with an embodiment.

FIG. 3 is a sectional elevation view of a blow molded container madefrom the preform of FIG. 2 in accordance with an embodiment.

FIG. 4 is a perspective view of a packaged beverage made in accordancewith an embodiment.

FIG. 5 is a schematic illustration of a process for the production of anenhanced gas barrier additive in accordance with an embodiment.

FIG. 6 is a schematic illustration of a process for the production of anenhanced gas barrier additive in accordance with an embodiment.

FIG. 7 is a graph illustrating the percent average bottle creep for blowmolded containers made in accordance with an embodiment.

DETAILED DESCRIPTION

A polyester container with enhanced gas barrier properties and a methodfor making a polyester container with enhanced gas barrier propertiesare provided herein. Generally described, the polyester containercomprises a polyester composition comprising a polyester and a gasbarrier enhancing additive having the chemical structure of Formula I orFormula II:

wherein X and X⁶, independent of one another, comprise hydrogen, halide,heteroatom, hydroxyl, amino, amido, alkylamino, arylamino, alkoxy,aryloxy, nitro, acyl, cyano, sulfo, sulfato, mercapto, imino, sulfonyl,sulfenyl, sulfinyl, sulfamoyl, phosphonyl, phosphinyl, phosphoryl,phosphino, thioester, thioether, anhydride, oximno, hydrazino, carbamyl,phosphonic acid, phosphonato, or a C₁-C₁₀ monovalent hydrocarbon whichmay be unsubstituted or substituted with one or more functionalmoieties;

wherein X¹, X², X³, X⁴, and X⁵, independent of one another, comprise aheteroatom or a C₁-C₁₀ divalent hydrocarbon, wherein each heteroatom orwhich may be unsubstituted or substituted with one or more functionalmoieties or one or more C₁-C₁₀ hydrocarbyls that may be unsubstituted orsubstituted with one or more functional moieties; and

wherein s, t, u, and v, independent of one another, may be a number from0 to 10;

wherein when X³ comprises a C₆ or C₁₀ divalent aromatic hydrocarbon, Xand X⁶, independent of one another, comprise a hydrogen, halide,heteroatom, hydroxyl, amino, amido, alkylamino, arylamino, alkoxy,aryloxy, nitro, acyl, cyano, sulfo, sulfato, mercapto, imino, sulfonyl,sulfenyl, sulfinyl, sulfamoyl, phosphonyl, phosphinyl, phosphoryl,phosphino, thioester, thioether, anhydride, oximno, hydrazino, carbamyl,phosphonic acid, phosphonato, or a C₃-C₁₀ monovalent cyclic orheterocyclic non-aryl hydrocarbon which may be unsubstituted orsubstituted with one or more functional moieties.

Polyester containers and methods for making such containers made inaccordance with the embodiments provided herein are further describedbelow and in accompanying FIGS. 1-7.

I. Polyester Composition

The polyester compositions and containers provided herein may beapplicable to any polyester and may be suitable for uses in which a highgas barrier is desirable. Non-limiting examples of suitable polyestersfor use in the embodiments provided herein include PET copolymers,polyethylene naphthalate (PEN), polyethylene isophthalate, and the like.PET copolymers are particularly useful because they are used for manybarrier applications, such as films and containers. Suitable containersinclude, but are not limited to, bottles, drums, carafes, coolers, andthe like.

Polyesters, including PET copolymers, have free volume between thepolymer chains. As is known to those skilled in the art, the amount offree volume in polyesters, such as PET copolymers, determines theirbarrier to gas molecules. The lower the free volume, the lower the gasdiffusion, and the higher the barrier to gas molecules. Desirably, thegas barrier enhancing additive is at least partially disposed in thefree volume of the polyester between the polyester chains.

PET copolymers suitable for use in embodiments of this invention maycomprise a diol component having repeat units from ethylene glycol and adiacid component having repeat units from terephthalic acid. Inparticular embodiments, the PET copolymer has less than 20 percentdiacid modification, less than 10 percent glycol modification, or both,based on 100 mole percent diacid component and 100 mole percent diolcomponent. Such PET copolymers are well known.

The polyester may be made using any suitable polycondensation catalysts;however, Applicants previously discovered that specific polycondensationcatalysts may be particularly suited for use with gas barrier enhancingadditives. Such polycondensation catalysts are disclosed in U.S. PatentPublication No. 2006/0275568. In one embodiment, the polyester may bemade using at least one first polycondensation catalyst selected fromthe group consisting of metals in groups 3, 4, 13, and 14 of thePeriodic Table. The polyester composition may comprise a catalystresidue remaining in the polyester from formation of the polyester andthe catalyst residue may comprise at least a portion of the at least onefirst polycondensation catalyst. In some embodiments, the catalystresidue may be present in the polyester composition in an amount up to250 ppm, and is preferably less.

The gas barrier enhancing additive and the polyester may undergo atransesterification reaction and thereby cause problems in containerapplications, such as lowering the I.V. of the polyester composition tounacceptable levels. Transesterification reaction in PET copolymer resinis believed to be catalyzed by the residual polycondensation catalyst.Accordingly, in one embodiment the residual polycondensation catalyst inthe polyester may be deactivated. One approach to deactivating thesecatalysts has been to add catalyst deactivating compounds, such asphosphorus containing compounds, to the polyester composition. Once thecatalysts are deactivated, they will not catalyze thetransesterification reaction and such reaction will be slowed downduring the melt processing of the polyester, such as PET copolymer, andgas barrier enhancing additive blend. The phosphorus containingcompounds include both organic and inorganic compounds. Examples includebut are not limited to phosphoric acid, polyphosphoric acid, andtris(2,4-di-t-butylphenyl) phosphite, tris monononylphenyl phosphite.

The polycondensation catalyst deactivating agent optionally may be addedto the polyester composition in an amount sufficient to deactivate thepolycondensation catalyst residue in the polyester composition so thatthe gas barrier enhancing additive is able to sufficiently enhance thegas barrier properties of the polyester composition and the resultingpolyester container. For example, these additives may be added to thepolyester composition in amounts less than 2000 ppm. In accordance withone embodiment, the polycondensation catalyst deactivating agent may bepresent in the polyester composition in amount from about 10 to about500 ppm by weight of the polyester composition or in an amount fromabout 100 to about 500 ppm by weight of the polyester composition.

Despite the addition of the polycondensation deactivating agents, theextent of the deactivation of the polycondensation remains unclear andmay not be sufficient to eliminate the degradation of the polyesterthrough reaction with the barrier enhancing additives when certainpolycondensation catalysts are used in the formation of the polyester bypolycondensation reaction. Accordingly, in other embodiments thepolyester composition may comprise a second polycondensation catalystselected from the group consisting of cobalt, antimony, zinc, manganese,magnesium, cesium, calcium, and cadmium. Those skilled in the art shouldappreciate that the amount of the second polycondensation catalyst whichis present in the polyester composition should be maintained belowlevels which may significantly lower the I.V. of the polyestercomposition below acceptable levels. Accordingly, in one embodiment thesecond polycondensation catalyst may be present in the polyestercomposition in an amount up to 3 ppm of the polyester composition.Specifically, the reactivity of traditional polycondensation catalystssuch as cobalt, antimony, zinc, manganese, magnesium, cesium, calcium,calcium, and cadmium is not mitigated to the extent necessary to makeuse of the phosphorus-based deactivating agents a viable alternativecompared to substantial reduction or elimination of the metal catalystresidues containing cobalt, antimony, zinc, manganese, magnesium,cesium, calcium, or cadmium.

Reaction between the gas barrier enhancing additive and the polyestercomposition can reduce the I.V. of the polyester composition andresulting container preform. PET with a significantly lower I.V. cannotbe used in blow molding containers, such as beverage containers, becauselower I.V. PET makes containers with poor mechanical performance, suchas creep, drop impact resistance, and the like. Still further, PETcontainers made from lower I.V. PET generally have poor stress crackingresistance for carbonated soft drink applications, which is undesirablein container applications. In order to prepare container preforms andcontainers with adequate physical properties and an I.V. suitable forefficient molding of the preforms and blow molding of such preforms intocontainers, the polyester composition desirably has an I.V. of at least0.65, more preferably from about 0.65 to about 1.0, and even morepreferably from about 0.70 to about 0.86. The units for I.V. herein areall in dL/g measured according to ASTM D4603-96, in which the I.V. ofPET based resin is measured at 30° C. with 0.5 weight percentconcentration in a 60/40 (by weight) phenol/1,1,2,2-tetrachloroethanesolution.

As discussed above, polyester having residual catalysts with minimal orno cobalt, antimony, zinc, manganese, magnesium, cesium, calcium, andcadmium substantially alleviates reduction in I.V. Total cobalt,antimony, zinc, manganese, magnesium, cesium, calcium, and cadmiumcontent is desirably less than 3 ppm. According to a particularembodiment, suitable gas barrier enhancing additives for PET polymersand copolymers are blended with polyester having titanium andaluminum-based metal catalyst residues without the presence of residuescontaining cobalt, antimony, zinc, manganese, magnesium, cesium,calcium, or cadmium. The periodicity of the elements in the modernperiodic table suggests that similar chemical reactivity existsthroughout a group. As such, zirconium and halfnium may be useful asanalogs for titanium catalysts, and gallium, indium, and thallium may beuseful analogs of aluminum. Germanium, tin, and lead from group 14 maybe suitable.

In a particular embodiment, a polyester composition comprises apolyester and a gas barrier enhancing additive, which is furtherdescribed below. The gas barrier enhancing additive of the polyestercomposition enhances the gas barrier properties of the polyestercomposition at low loading levels, desirably in the range of about 0.1to about 10 weight percent of the polyester composition, more desirablyin the range of about 1 to about 6 weight percent of the polyestercomposition, and still more desirably in the range of about 2 to about 4weight percent of the polyester composition. At low loading levels, aslight barrier improvement factor (BIF) occurs. Although the improvementin the BIF may be substantial at high loading levels, the physicalproperties of the PET deteriorate and make forming a container moredifficult. The BIF is a measure of enhanced gas barrier properties (theratio of the gas transmission rate of a polyester composition without anadditive to the gas transmission rate of a polyester composition with anadditive). The BIF that can be observed by the use of gas barrierenhancing additives provided herein can range from about 1.05 to greaterthan 2, with typical values of BIF being from about 1.15 to about 1.5.

According to an embodiment, the polyester composition comprises apolyester present in the polyester composition in an amount in the rangeof about 99.9 to about 90 weight percent of the polyester compositionand a gas barrier enhancing additive present in the polyestercomposition in an amount in the range of about 0.1 to about 10 weightpercent of the polyester composition.

In particular embodiments, the polyester compositions provided hereinmay further comprise a suitable creep control agent. Suitable creepcontrol agents are known to those skilled in the art for enhancingmechanical properties of polyesters; however, Applicants havesurprisingly discovered that the combination of creep control agentswith the gas barrier enhancing additives provided herein furtherenhances the gas barrier properties of the polyester composition. Suchcreep control agents are further described below, and are described indetail in U.S. Pat. No. 8,110,265, the disclosure of which isincorporated herein by reference in its entirety.

II. Gas Barrier Enhancing Additives

The gas barrier enhancing additives provided herein generally comprisegas barrier additives having decreased volatility as compared topreviously discovered gas barrier additives. As used herein, the terms“gas barrier enhancing additive,” “gas barrier enhancement additive,”and “gas barrier additive” are synonymous and may be usedinterchangeably.

In an embodiment, a gas barrier enhancing additive having the chemicalstructure of Formula I or Formula II is provided:

wherein X and X⁶, independent of one another, comprise hydrogen, halide,heteroatom, hydroxyl, amino, amido, alkylamino, arylamino, alkoxy,aryloxy, nitro, acyl, cyano, sulfo, sulfato, mercapto, imino, sulfonyl,sulfenyl, sulfinyl, sulfamoyl, phosphonyl, phosphinyl, phosphoryl,phosphino, thioester, thioether, anhydride, oximno, hydrazino, carbamyl,phosphonic acid, phosphonato, or a C₁-C₁₀ monovalent hydrocarbon whichmay be unsubstituted or substituted with one or more functionalmoieties;

wherein X¹, X², X³, X⁴, and X⁵, independent of one another, comprise aheteroatom or a C₁-C₁₀ divalent hydrocarbon, wherein each heteroatom orC₁-C₁₀ divalent hydrocarbon may be unsubstituted or substituted with oneor more functional moieties or one or more C₁-C₁₀ hydrocarbyls that maybe unsubstituted or substituted with one or more functional moieties;and

wherein s, t, u, and v, independent of one another, may be a number from0 to 10.

In particular embodiments, when X³ may comprise a C₆ or C₁₀ divalentaromatic hydrocarbon, X and X⁶, independent of one another, may comprisea hydrogen, halide, heteroatom, hydroxyl, amino, amido, alkylamino,arylamino, alkoxy, aryloxy, nitro, acyl, cyano, sulfo, sulfato,mercapto, imino, sulfonyl, sulfenyl, sulfinyl, sulfamoyl, phosphonyl,phosphinyl, phosphoryl, phosphino, thioester, thioether, anhydride,oximno, hydrazino, carbamyl, phosphonic acid, phosphonato, or a C₃-C₁₀monovalent cyclic or heterocyclic non-aryl hydrocarbon which may beunsubstituted or substituted with one or more functional moieties.

In an embodiment of the compound of Formula I, wherein X and X⁶ eachcomprise a phenyl group, the gas barrier additive comprises a compoundhaving the chemical structure:

In an embodiment of the compound of Formula I, wherein X and X⁶ eachcomprise a phenyl group and s and v are 0, the gas barrier additivecomprises a compound having the chemical structure:

In an embodiment of the compound of Formula I, wherein X and X⁶ eachcomprise a phenyl group and s, t, u, and v are 0, the gas barrieradditive comprises a compound having the chemical structure:

In an embodiment of the compound of Formula I, wherein X and X⁶ eachcomprise a phenyl group, s, t, u and v are 0, and X³ comprises adivalent isosorbide, the gas barrier additive comprises dibenzoylisosorbide, a compound having the chemical structure:

In an embodiment of the compound of Formula I, wherein X and X⁶ comprisea phenyl group, s, t, u, and v are 0, and X³ comprises a divalentcyclohexane, the gas barrier additive comprises a compound having thechemical structure:

In an embodiment of the compound of Formula I, wherein X and X⁶ eachcomprise a phenyl group, s and v are 0, t and u are 1, and X² and X⁴each comprise a divalent C₁ hydrocarbon, the gas barrier additivecomprises a compound having the chemical structure:

In an embodiment of the compound of Formula I, wherein X and X⁶ eachcomprise a phenyl group, s and v are 0, t and u are 1, X² and X⁴ eachcomprise a divalent C₁ hydrocarbon, and X³ comprises a divalent hydrobi-furan, the gas barrier additive comprises a compound having thechemical structure:

In an embodiment of the compound of Formula I, wherein X and X⁶ comprisea phenyl group, s and v are 0, t and u are 1, X² and X⁴ comprise adivalent C₁ hydrocarbon, and X³ comprises a divalent cyclohexane, thegas barrier additive comprises a compound having the chemical structure:

In an embodiment of the compound of Formula I, wherein X and X⁶ eachcomprise a naphthyl group, the gas barrier additive comprises a compoundhaving the chemical structure:

In an embodiment of the compound of Formula I, wherein X and X⁶ eachcomprise a naphthyl group and s and v are 0, the gas barrier additivecomprises a compound having the chemical structure:

In an embodiment of the compound of Formula I, wherein X and X⁶ eachcomprise a naphthyl group, s and v are 0, t and u are 1, and X² and X⁴each comprise a divalent C₁ hydrocarbon, the gas barrier additivecomprises a compound having the chemical structure:

In an embodiment of the compound of Formula I, wherein X and X⁶ eachcomprise a naphthyl group, s and v are 0, t and u are 1, each X² and X⁴comprise a divalent C₁ hydrocarbon, and X³ comprises a divalentcyclohexane which may be ortho-, meta-, or para-substituted, the gasbarrier additive comprises a compound having the chemical structure:

For example, in a particular embodiment wherein the divalent cyclohexaneis para-substituted, the gas barrier additive comprisescyclohexane-1,4-diylbis(methylene)di-2-naphthoate, a compound having thechemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a cyclohexyl group, the gas barrier additive comprises acompound having the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a cyclohexyl group and s and v are 0, the gas barrier additivecomprises a compound having the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a cyclohexyl group and s, t, u, and v are 0, the gas barrieradditive comprises a compound having the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a cyclohexyl group, s, t, u, and v are 0, and X³ comprises adivalent benzene which may be ortho-, meta-, or para-substituted, thegas barrier additive comprises a compound having the chemical structure:

For example, in a particular embodiment wherein the divalent benzene ispara-substituted, the gas barrier additive comprises dicyclohexylterephthalate, a compound having the chemical structure:

In another embodiment the divalent benzene may be meta-substituted suchthat the gas barrier additive comprises dicyclohexyl isophthalate, acompound having the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a cyclohexyl group, s, t, u, and v are 0, and X³ comprises adivalent naphthalene which may be substituted at any position on eitherring (e.g., 1, 2, 3, 4, 5, 6, 7, or 8), the gas barrier additivecomprises a compound having the chemical structure:

For example, in a particular embodiment wherein the divalent naphthaleneis substituted at the 2 and 6 positions, the gas barrier additivecomprises dicyclohexyl naphthalene-2,6-dicarboxylate, a compound havingthe chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a benzoate group, the gas barrier additive comprises a compoundhaving the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a benzoate group and t and u are 0, the gas barrier additivecomprises a compound having the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a benzoate group, t and u are 0, s and v are 1, and X¹ and X⁵each comprise a divalent C₁ hydrocarbon, the gas barrier additivecomprises a compound having the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a benzoate group, t and u are 0, s and v are 1, and X¹ and X⁵each comprise a divalent C₁ hydrocarbon, and X³ is a divalent benzenewhich may be ortho-, meta-, or para-substituted, the gas barrieradditive comprises a compound having the chemical structure:

In a particular embodiment wherein the divalent benzene ispara-substituted, the gas barrier additive comprisesbis(2-(benzoyloxy)ethyl) terephthalate), a compound having the chemicalstructure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a benzoate group, the gas barrier additive comprises a compoundhaving the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a benzoate group, s and v are 2, and X¹ and X⁵ each comprise adivalent C₁ hydrocarbon, the gas barrier additive comprises a compoundhaving the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a benzoate group, s and v are 2, X¹ and X⁵ each comprise adivalent C₁ hydrocarbon, t and u are 1, and X² and X⁴ each comprise adivalent benzoate which may be ortho-, meta-, or para-substituted, thegas barrier additive comprises a compound having the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise a benzoate group, s and v are 2, X¹ and X⁵ each comprise adivalent C₁ hydrocarbon, t and u are 1, X² and X⁴ each comprise adivalent benzoate which may be ortho-, meta-, or para-substituted, andX³ comprises a divalent C₂ hydrocarbon, the gas barrier additivecomprises a compound having the chemical structure:

In a particular embodiment wherein the divalent benzoates aremeta-substituted, the gas barrier additive comprisesbis(2-(benzoyloxy)ethyl)′-ethane-1,2-diyl diisophthalate, a compoundhaving the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise an aryloxy group (e.g., a phenoxy group), the gas barrieradditive comprises a compound having the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise an aryloxy group (e.g., a phenoxy group), t and u are 0, thegas barrier additive comprises a compound having the chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise an aryloxy group (e.g., a phenoxy group), t and u are 0, and X³comprises a divalent benzene which may be ortho-, meta-, orpara-substituted, the gas barrier additive comprises a compound havingthe chemical structure:

In an embodiment of the compound of Formula II, wherein X and X⁶ eachcomprise an aryloxy group (e.g., a phenoxy group), t and u are 0, s andv are 1, X¹ and X⁵ comprise a straight-chain divalent C₂ hydrocarbon,and X³ comprises a divalent benzene which may be ortho-, meta-, orpara-substituted, the gas barrier additive comprises a compound havingthe chemical structure:

For example, in a particular embodiment wherein the divalent benzene ispara-substituted, the gas barrier additive comprisesbis(2-phenoxyethyl)terephthalate (PEM), a compound having the chemicalstructure:

As used herein, the term “heteroatom” refers to any atom other thancarbon or hydrogen. Typically, the heteroatom comprises nitrogen,oxygen, or sulfur.

The term “hydrocarbyl,” as used herein, is used to describe a monovalenthydrocarbon that may form one bond with another atom within a singlechemical compound. The term “divalent hydrocarbon,” as used herein, isused to describe a hydrocarbon which may form two bonds to either oneother atom as a double bond or two other atoms as separate single bonds,all within a single chemical compound. The term “triavalenthydrocarbon,” as used herein, is used to describe a hydrocarbon whichmay form three bonds to either one atom as a triple bond, two otheratoms as a double and single bond, or three atoms as separate singlebonds, all within a single chemical compound. A “tetravalent carbonatom,” as used herein, is used to describe a carbon atom that may formfour bonds to either two other atoms as one triple bond and one singlebond, two other atoms as two double bonds, three different atoms as onedouble bond and two single bonds, or four different atoms as fourseparate single bonds, all within a single chemical compound.

The terms “hydrocarbon” and “hydrocarbyl,” as used herein, include analiphatic group, an aromatic or aryl group, a cyclic group, aheterocyclic group, or any combination thereof and any substitutedderivative thereof, including but not limited to, a halide, an alkoxide,or an amide-substituted derivative thereof. Also included in thedefinition of the hydrocarbyl are any unsubstituted, branched, or linearanalogs thereof. The hydrocaryl may be substituted with one or morefunctional moieties as described hereinbelow.

Examples of aliphatic groups, in each instance, include, but are notlimited to, an alkyl group, a cycloalkyl group, an alkenyl group, acycloalkenyl group, an alkynyl group, an alkadienyl group, a cyclicgroup, and the like, and includes all substituted, unsubstituted,branched, and linear analogs or derivatives thereof. Examples of alkylgroups include, but are not limited to, methyl, ethyl, propyl,isopropyl, n-butyl, t-butyl, isobutyl, pentyl, hexyl, isohexyl, heptyl,4,4-dimethylpentyl, octyl, 2,2,4-trimethylpentyl, nonyl, and decyl.Cycloalkyl moieties may be monocyclic or multicyclic, and examplesinclude cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and adamantyl.Additional examples of alkyl moieties have linear, branched and/orcyclic portions (e.g., 1-ethyl-4-methyl-cyclohexyl). Representativealkenyl moieties include vinyl, allyl, 1-butenyl, 2-butenyl,isobutylenyl, 1-pentenyl, 2-pentenyl, 3-methyl-1-butenyl,2-methyl-2-butenyl, 2,3-dimethyl-2-butenyl, 1-hexenyl, 2-hexenyl,3-hexenyl, 1-heptenyl, 2-heptenyl, 3-heptenyl, 1-octenyl, 2-octenyl,3-octenyl, 1-nonenyl, 2-nonenyl, 3-nonenyl, 1-decenyl, 2-decenyl and3-decenyl. Representative alkynyl moieties include acetylenyl, propynyl,1-butynyl, 2-butynyl, 1-pentynyl, 2-pentynyl, 3-methyl-1-butynyl,4-pentynyl, 1-hexynyl, 2-hexynyl, 5-hexynyl, 1-heptynyl, 2-heptynyl,6-heptynyl, 1-octynyl, 2-octynyl, 7-octynyl, 1-nonynyl, 2-nonynyl,8-nonynyl, 1-decynyl, 2-decynyl and 9-decynyl.

Examples of aryl or aromatic moieties include, but are not limited to,anthracenyl, azulenyl, biphenyl, fluorenyl, indan, indenyl, naphthyl,phenyl, 1,2,3,4-tetrahydro-naphthalene, and the like, includingsubstituted derivatives thereof, in each instance having from 6 to about10 carbons. Substituted derivatives of aromatic compounds include, butare not limited to, tolyl, xylyl, mesityl, and the like, including anyheteroatom substituted derivative thereof. Examples of cyclic groups, ineach instance, include, but are not limited to, cycloparaffins,cycloolefins, cycloacetylenes, arenes such as phenyl, bicyclic groupsand the like, including substituted derivatives thereof. Thusheteroatom-substituted cyclic groups and bicyclic groups such as furanyland isosorbyl are also included herein.

In each instance, aliphatic and cyclic groups are groups comprising analiphatic portion and a cyclic portion, examples of which include, butare not limited to, groups such as: —(CH₂)_(m)C₆H_(q)M_(5−q) wherein mis an integer from 1 to about 10, q is an integer from 1 to 5,inclusive; (CH₂)_(m)C₆H_(q)R_(10−q) wherein m is an integer from 1 toabout 10, q is an integer from 1 to 10, inclusive; and(CH₂)_(m)C₅H_(q)R_(9−q) wherein m is an integer from 1 to about 10, q isan integer from 1 to 9, inclusive. In each instance and as definedabove, M is independently selected from: an aliphatic group; an aromaticgroup; a cyclic group; any combination thereof; any substitutedderivative thereof, including but not limited to, a halide-, analkoxide-, or an amide-substituted derivative thereof any one of whichhas from 1 to about 10 carbon atoms; or hydrogen. In one aspect,aliphatic and cyclic groups include, but are not limited to: —CH₂C₆H₅;—CH₂C₆H₄F; —CH₂C₆H₄Cl; —CH₂C₆H₄Br; —CH₂C₆H₄I; —CH₂C₆H₄OMe; —CH₂C₆H₄OEt;—CH₂C₆H₄NH₂; —CH₂C₆H₄NMe₂; —CH₂C₆H₄NEt₂; —CH₂CH₂C₆H₅; —CH₂CH₂C₆H₄F;—CH₂CH₂C₆H₄Cl; —CH₂CH₂C₆H₄Br; —CH₂CH₂C₆H₄I; —CH₂CH₂C₆H₄OMe;—CH₂CH₂C₆H₄OEt; —CH₂CH₂C₆H₄NH₂; —CH₂CH₂C₆H₄NMe₂; —CH₂CH₂C₆H₄NEt₂; anyregioisomer thereof, or any substituted derivative thereof.

In each instance, the heterocycle comprising at least one N-, O-, orS-heteroatom may be selected from the group consisting of: morpholinyl,thiomorpholinyl, thiomorpholinyl S-oxide, thiomorpholinyl S,S-dioxide,piperazinyl, homopiperazinyl, pyrrolidinyl, pyrrolinyl,tetrahydropyranyl, piperidinyl, tetrahydrofuranyl, tetrahydrothienyl,homopiperidinyl, homomorpholinyl, homothiomorpholinyl,homothiomorpholinyl S,S-dioxide, oxazolidinonyl, dihydropyrazolyl,dihydropyrrolyl, dihydropyrazinyl, dihydropyridinyl, dihydropyrimidinyl,dihydrofuryl, dihydropyranyl, tetrahydrothienyl S-oxide,tetrahydrothienyl S,S-dioxide, and homothiomorpholinyl S-oxide,pyridinyl, pyrimidinyl, quinolinyl, benzothienyl, indolyl, indolinyl,pryidazinyl, pyrazinyl, isoindolyl, isoquinolyl, quinazolinyl,quinoxalinyl, phthalazinyl, imidazolyl, isoxazolyl, pyrazolyl, oxazolyl,thiazolyl, indolizinyl, indazolyl, benzothiazolyl, benzimidazolyl,benzofuranyl, furanyl, thienyl, pyrrolyl, oxadiazolyl, thiadiazolyl,triazolyl, tetrazolyl, oxazolopyridinyl, imidazopyridinyl, isothiazolyl,naphthyridinyl, cinnolinyl, carbazolyl, beta-carbolinyl, isochromanyl,chromanyl, tetrahydroisoquinolinyl, isoindolinyl,isobenzotetrahydrofuranyl, isobenzotetrahydrothienyl, isobenzothienyl,isosorbyl, benzoxazolyl, pyridopyridinyl, benzotetrahydrofuranyl,benzotetrahydrothienyl, purinyl, benzodioxolyl, triazinyl, phenoxazinyl,phenothiazinyl, pteridinyl, benzothiazolyl, imidazopyridinyl,imidazothiazolyl, dihydrobenzisoxazinyl, benzisoxazinyl, benzoxazinyl,dihydrobenzisothiazinyl, benzopyranyl, benzothiopyranyl, coumarinyl,isocoumarinyl, chromonyl, chromanonyl, pyridinyl-N-oxide,tetrahydroquinolinyl, dihydroquinolinyl, dihydroquinolinonyl,dihydroisoquinolinonyl, dihydrocoumarinyl, dihydroisocoumarinyl,isoindolinonyl, benzodioxanyl, benzoxazolinonyl, pyrrolyl N-oxide,pyrimidinyl N-oxide, pyridazinyl N-oxide, pyrazinyl N-oxide, quinolinylN-oxide, indolyl N-oxide, indolinyl N-oxide, isoquinolyl N-oxide,quinazolinyl N-oxide, quinoxalinyl N-oxide, phthalazinyl N-oxide,imidazolyl N-oxide, isoxazolyl N-oxide, oxazolyl N-oxide, thiazolylN-oxide, indolizinyl N-oxide, indazolyl N-oxide, benzothiazolyl N-oxide,benzimidazolyl N-oxide, pyrrolyl N-oxide, oxadiazolyl N-oxide,thiadiazolyl N-oxide, triazolyl N-oxide, tetrazolyl N-oxide,benzothiopyranyl S-oxide, or benzothiopyranyl S,S-dioxide.

The term alkoxy, as used herein, and unless otherwise specified, refersto a moiety of the structure —O-alkyl, wherein alkyl is as definedabove.

The term acyl, as used herein, refers to a group of the formula C(O)R′,wherein R′ is an alkyl, aryl, heteroaryl, heterocyclic, alkaryl oraralkyl group, or substituted alkyl, aryl, heteroaryl, heterocyclic,aralkyl or alkaryl, wherein these groups are as defined above.

Unless otherwise indicated, the term “substituted,” when used todescribe a chemical structure or moiety, refers to a derivative of thatstructure or moiety wherein one or more of its hydrogen atoms issubstituted with a chemical moiety or functional group. Non-limitingexamples of suitable functional moieties, as used herein, includehalide, hydroxyl, amino, amido, alkylamino, arylamino, alkoxy, aryloxy,nitro, acyl, cyano, sulfo, sulfato, mercapto, imino, sulfonyl, sulfenyl,sulfinyl, sulfamoyl, phosphonyl, phosphinyl, phosphoryl, phosphino,thioester, thioether, anhydride, oximno, hydrazino, carbamyl, phosphonicacid, phosphonato, ether, ketone, ester, and any other viable functionalgroup.

III. Creep Control Agents

In one aspect of this disclosure, the polyester composition comprises acreep control agent having the chemical structure of Formula I:

wherein R¹, R², R³, and R⁴, independent of one another, may comprise aheteroatom, a tetravalent carbon atom, or a C₁-C₃ divalent or trivalenthydrocarbon; wherein each heteroatom, tetravalent carbon atom, or C₁-C₃divalent or trivalent hydrocarbon may be unsubstituted or substitutedwith one or more functional moieties or one or more C₁-C₁₀ hydrocarbylsthat may be unsubstituted or substituted with one or more functionalmoieties;

wherein i, ii, iii, iv, v, and vi, independent of one another, comprisea single, double, or triple bond; wherein when i is a double bond, iiand vi are single bonds; wherein when ii is a double bond, i and iii aresingle bonds; wherein when iii is a double bond, ii and iv are singlebonds; wherein when iv is a double bond iii and v are single bonds;wherein when v is a double bond, iv and vi are single bonds; whereinwhen vi is a double bond, i and v are single bonds; wherein vii may be asingle bond, double bond, or no bond at all connects R³ and R⁴;

wherein m, n, o, and p, independent of one another, may be 0 or 1;wherein when m is 0, bonds ii and iii form a single continuous bond;wherein when n is 0, bonds vi and v form a single continuous bond;wherein when o is 0, R⁴ is bonded to R¹ by a single bond; and whereinwhen p is 0, R³ is bonded to R² by a single bond.

In a particular embodiment of the compound of Formula I, wherein m, n,o, and p are 0; and i, ii/iii, iv, and v/vi are single bonds; the creepcontrol agent comprises cyclobutane-1,2,3,4-tetracarboxylic aciddianhydride, a compound having the chemical structure:

In another embodiment of the compound of Formula I, wherein n, o, and pare 0; m is 1; i, ii, iii, iv, and v/vi are single bonds; and R¹ isoxygen; the creep control agent comprises2,3,4,5-tetrahydro-2,3,4,5-tetracarboxylic-furan dianhydride, a compoundhaving the chemical structure:

In yet another embodiment of the compound of Formula I, wherein m and nare 1; o and p are 0; R¹ and R² are trivalent hydrocarbons comprising 1carbon atom; i, iii, and v are double bonds; and ii, iv, and vi aresingle bonds; the creep control agent comprises pyromelliticdianhydride, a compound having the chemical structure:

In yet another embodiment of the compound of Formula I, wherein m, n, o,and p are 1; R¹, R², R³, and R⁴ are trivalent hydrocarbons comprising 1carbon atom; i, ii, iii, iv, v, and vi are single bonds; and vii is adouble bond; the creep control agent comprisesbicyclo[2.2.2]oct-3,4-ene-1,2,5,6-tetracarboxylic acid dianhydride, acompound having the chemical structure:

In another aspect of this disclosure, the polyester compositioncomprises a creep control agent having the chemical structure of FormulaII:

wherein A, A′, A″, E, D, G, G′, G″, L, and J, independent of oneanother, may comprise a heteroatom, a tetravalent carbon atom, or aC₁-C₃ divalent or trivalent hydrocarbon; wherein each heteroatom,tetravalent carbon atom, or C₁-C₃ divalent or trivalent hydrocarbon maybe unsubstituted or substituted with one or more functional moieties orone or more C₁-C₁₀ hydrocarbyls that may be unsubstituted or substitutedwith one or more functional moieties;

wherein i, ii, iii, iv, v, vi, vii, viii, ix, and x, independent of oneanother, may comprise a single or double bond; wherein when i is adouble bond, ii and v are single bonds; wherein when ii is a doublebond, i and iii are single bonds; wherein when iii is a double bond, iiand iv are single bonds; wherein when iv is a double bond, iii and v aresingle bonds; wherein when v is a double bond, i and iv are singlebonds; wherein when vi is a double bond, vii and x are single bonds;wherein when vii is a double bond, vi and viii are single bonds; whereinwhen viii is a double bond, vii and ix are single bonds; wherein when ixis a double bond, viii and x are single bonds; wherein when x is adouble bond, vi and ix are single bonds;

wherein b, c, d, e, f, g, h, i, j, and k, independent of one another maybe 0 or 1;

wherein a may be 0 or 1; and

wherein R⁵ may be a heteroatom or a C₁-C₁₀ divalent hydrocarbon that maybe unsubstituted or substituted with one or more functional moieties,one or more heteroatoms, or one or more C₁-C₁₀ hydrocarbyls that may beunsubstituted or substituted with one or more functional moieties.

In one embodiment of the compound of Formula II, wherein b, c, d, e, f,g, h, i, j, and k, are 1; a is 0; E and L are divalent hydrocarbonscomprising 1 carbon atom; A′, D, J, G′ are trivalent hydrocarbonscomprising 1 carbon atom; A and G″ are oxygen; A″ and G are nitrogen; i,ii, iv, v, vi, viii, ix, and x are single bonds; iii and vii are doublebonds; and the ring comprising A, A′, A″, D, and E is bonded to the ringcomprising G, G′, G″, L, and J via a single bond between D and J, thecreep control agent is 4,′-bisoxazoline, a compound having the chemicalstructure:

In another embodiment of the compound of Formula II, wherein b, c, d, e,f, g, h, i, j, and k are 1; a is 0; A′, D, J, G′ are trivalenthydrocarbons comprising 1 carbon atom; E and L are divalent hydrocarbonscomprising 1 carbon atom; A and G are nitrogen; A″ and G″ are oxygen; iiand vii are double bonds; i, iii, iv, v, vi, viii, ix, and x are singlebonds; and the ring comprising A, A′, A″, D, and E is bonded to the ringcomprising G, G′, G″, L, and J via a single bond between D and J, thecreep control agent is 4,4′-bisoxazoline, a compound having the chemicalstructure:

In yet another embodiment of the compound of Formula II, wherein b, c,d, e, f, g, h, i, j, and k are 1; a is 0; A″ and G″ are oxygen; E and Lare nitrogen; J and D are tetravalent carbon atoms; A, A′, G and G′ aredivalent hydrocarbons comprising 1 carbon atom; v and x are doublebonds; i, ii, iii, iv, vi, vii, viii, and ix are single bonds; and thering comprising A, A′, A″, D, and E is bonded to the ring comprising G,G′, G″, L, and J, via a single bond between D and J, the creep controlagent is 2,2′-bix(2-oxazoline), a compound having the chemicalstructure:

In yet another embodiment of the compound of Formula II, wherein a, b,c, d, e, f, g, h, i, j, and k are 1; A′, D, J, G′ are trivalenthydrocarbons comprising 1 carbon atom; R⁵, E and L are divalenthydrocarbons comprising 1 carbon atom; A and G are nitrogen; A″ and G″are oxygen; ii and vii are double bonds; i, iii, iv, v, vi, viii, ix,and x are single bonds; and R⁵ is bonded to D and J, the creep controlagent is bis(4,5-dihydrooxazol-5-yl)methane, a compound having thechemical structure:

In yet another embodiment of the compound of Formula II, wherein d, e,f, g, k, j, and a are 1; b, c, h, and i are 0; E and L are oxygen; R⁵,A″, and G″ are divalent hydrocarbons comprising 1 carbon atom; D, and Jare trivalent hydrocarbons comprising carbon atom; iv, v, ix, and x aresingle bonds; E and A″ are bonded directly together via a single bond; Land G″ are bonded together via a single bond; and R⁵ is bonded to D andJ, the creep control agent is bis(4,5-dihydrooxaol-5-yl)methane, acompound having the chemical structure:

In another aspect of this disclosure, the polyester compositioncomprises a creep control agent having the chemical structure of FormulaIII:

wherein R⁶ and R⁷, independent of one another, may comprise a C₁-C₅divalent hydrocarbon that may be unsubstituted or substituted with oneor more functional moieties, one or more heteroatoms, or one or moreC₁-C₁₀ hydrocarbyls that may be unsubstituted or substituted with one ormore functional moieties.

In one particular embodiment of the compound of Formula III, wherein R⁶and R⁷ are divalent hydrocarbons comprising 5 carbon atoms, the creepcontrol agent is bis-carpolactam carbonyl, a compound having thechemical structure:

In yet another aspect of this disclosure, the polyester compositioncomprises a creep control agent having the chemical structure of FormulaIV:

wherein A¹, A², R⁸, R⁹, and R¹⁰, independent of one another, maycomprise a heteroatom, a tetravalent carbon atom, a C₁-C₁° divalent ortrivalent hydrocarbon, or a C₁-C₁₀ hydrocarbyl that may be unsubstitutedor substituted with one or more functional moieties;

wherein each heteroatom, tetravalent carbon atom, or C₁-C₁₀ divalent ortrivalent hydrocarbon may be unsubstituted or substituted with one ormore functional moieties or one or more C₁-C₁° hydrocarbyls that may beunsubstituted or substituted with one or more functional moieties;

wherein m′, n′, and p′, independent of one another, may be 0 or 1;

wherein i, ii, and iii, independent of one another may be a single bondor a double bond;

wherein t, u, v, and w, independent of one another may be a single bond,double bond, or triple bond; and

wherein q, r, and s may be from 0 to 10,000.

In one particular embodiment of the compound of Formula IV, wherein q,r, p′, m′ are 0; s and n′ are 1; R⁸ is isobenzofuran-1,3-dione; i, ii,and iii are double bonds; the creep control agent isbiphenyl-2,3,2′,3′-tetracarboxylic acid dianhydride, a compound with thechemical structure:

In another particular embodiment of the compound of Formula IV, whereinq, and r are 0; s, p′, n′, and m′ are 1; R⁸ comprises a tetravalentcarbon atom; R⁹ comprises oxygen; R¹⁰ comprises isobenzofuran-1,3-dione;u, i, ii, and iii are double bonds; and v is a single bond, the creepcontrol agent is benzophenone-3,4,3′,4′-tetracarboxylic aciddianhydride, a compound with the chemical formula:

In another particular embodiment of the compound of Formula IV, whereinq and s are 1000; r and p′ are 0; m′ and n′ are 1; R⁸ is a trivalenthydrocarbon comprising 1 carbon atom; R¹⁰ is a divalent hydrocarboncomprising 1 carbon atom; t and v are single bonds; i, ii, and iii aredouble bonds; and A¹ is a methyl methacrylate monomer, the creep controlagent is a co-polymer of 5-vinylisobenzofuran-1,3-dione and methylmethacrylate (MMA), a co-polymer with the chemical formula:

In another particular embodiment of the compound of Formula IV, whereinq and s are 1000; r and p′ are 0; m′ and n′ are 1; R⁸ is a trivalenthydrocarbon comprising 1 carbon atom; R¹⁰ is a divalent hydrocarboncomprising one carbon atom; t and v are single bonds; i, ii, and iii aredouble bonds; and A¹ is a styrene monomer, the creep control agent is aco-polymer of 5-vinylisobenzofuran-1,3-dione and styrene, a co-polymerwith the chemical formula:

In yet another particular embodiment of the compound of Formula IV,wherein r, q, and s are 1000; p′ is 0; m′ and n′ are 1; R⁸ is atrivalent hydrocarbon comprising 1 carbon atom; R¹⁰ is a divalenthydrocarbon comprising one carbon atom; w, t, and v are single bonds; i,ii, and iii are double bonds; A¹ is a methyl methacrylate monomer; andA² is a styrene monomer, the creep control agent is a co-polymer ofmethyl methacrylate, 5-vinylisobenzofuran-1,3-dione, and styrene, aco-polymer with the chemical formula:

In another aspect of this disclosure, the polyester compositioncomprises a creep control agent having the chemical structure of FormulaV:

wherein R may comprise a heteroatom or a C₁-C₁₀ hydrocarbyl which may beunsubstituted or substituted with one or more functional moieties; and

wherein m″, n″, and o″, independent of one another, may be from 0 to1,000.

Formula V represents the chemical structure of Joncryl®-ADR, which issold by BASF Corporation, Florham Park, N.J., 07932. The molecularweight of the polymer represented by Formula V is below about 3000.

In a particular embodiment of the compound of Formula V, wherein m″, n″,and o″ are 100; and R is a methyl, the creep control agent is aco-polymer having the chemical structure:

In yet another aspect of this disclosure, the polyester compositioncomprises a creep control agent having the chemical structure of FormulaVI:

wherein R¹¹, R¹², R¹³, and R¹⁴, independent of one another, may comprisea heteroatom, a tetravalent carbon atom, or a C₁-C₃ divalent ortrivalent hydrocarbon; wherein each heteroatom, tetravalent carbon atom,or C₁-C₃ divalent or trivalent hydrocarbon may be unsubstituted orsubstituted with one or more functional moieties or one or more C₁-C₁₀hydrocarbyls that may be unsubstituted or substituted with one or morefunctional moieties; and

wherein i, ii, iii, iv, v, vi, vii, viii, ix, x, and xi, independent ofone another, are a single bond or double bond; wherein when i is adouble bond, ii and vi are single bonds; wherein when ii is a doublebond, i, iii, and vii are single bonds; wherein when iii is a doublebond, ii, iv, vii, and xi are single bonds; wherein when iv is a doublebond, iii, v, and xi are single bonds; wherein when v is a double bond,vi and iv are single bonds; wherein when vi is a double bond, i and vare single bonds; wherein when vii is a double bond, ii, iii, and viiiare single bonds; wherein when viii is a double bond, vi and ix aresingle bonds; wherein when ix is a double bond, viii and x are singlebonds; wherein when x is a double bond, ix and xi are single bonds;wherein when xi is a double bond, iv, x, and iii are single bonds.

In a particular embodiment of the compound of Formula VI, wherein R¹¹,R¹², R¹³, and R¹⁴ are trivalent hydrocarbons comprising one carbon atom;vi, ii, iv, viii, and x are double bonds; and i, iii, v, vii, ix aresingle bonds, the creep control agent is 1,4,5,8-tetracarboxylicacid-naphthalene dianhydride, a compound having the chemical formula:

In yet another aspect of this disclosure, the polyester compositioncomprises a creep control agent having the chemical structure of FormulaVII:

wherein R¹⁵, R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰, R²¹, and R²², independent of oneanother, may comprise a heteroatom, a tetravalent carbon atom, or aC₁-C₃ divalent or trivalent hydrocarbon; wherein each heteroatom,tetravalent carbon atom, or C₁-C₃ divalent or trivalent hydrocarbon maybe unsubstituted or substituted with one or more functional moieties orone or more C₁-C₁₀ hydrocarbyls that may be unsubstituted or substitutedwith one or more functional moieties; and

wherein i, ii, iii, iv, v, vi, vii, viii, ix, x, xi, xii, xiii, xiv, xv,xvi, xvii, xviii, xix, xx, xxi, xxii, independent of one another, are adouble bond or single bond; wherein when i is a double bond, ii and viare single bonds; wherein when ii is a double bond, i, iii, and vii aresingle bonds; wherein when iii is a double bond, ii, iv, vii, and xi aresingle bonds; wherein when iv is a double bond, iii, v, xi, and xii aresingle bonds; wherein when v is a double bond, vi, iv, and xii aresingle bonds; wherein when vi is a double bond, i and v are singlebonds; wherein when vii is a double bond, ii, iii and viii are singlebonds; wherein when viii is a double bond, vii and ix are single bonds;wherein when ix is a double bond, viii and x are single bonds; whereinwhen x is a double bond, ix, xi, and xiii are single bonds; wherein whenxi is a double bond, iii, iv, xiii and x are single bonds; wherein whenxii is a double bond, v, iv, xvi, and xiv are single bonds; wherein whenxiv is a double bond, xii, xvi, xv, and xix are single bonds; whereinwhen xv is a double bond, xiii, xvii, xiv, and xix are single bonds;when xiii is a double bond, xi, x, xv, and xvii are single bonds; whenxvi is a double bond, xii, xiv, and xviii are single bonds; wherein whenxviii is a double bond, xvi and xxi are single bonds; wherein when xxiis a double bond, xviii and xxii are single bonds; wherein when xxii isa double bond, xxi, xix, and xxiii are single bonds; wherein when xix isa double bond, xiv, xv, xxii, and xxiii are single bonds; wherein whenxxiii is a double bond, xix, xxii, and xxiv are single bonds; whereinwhen xxiv is a double bond, xxiii and xx are single bonds; wherein whenxx is a double bond, xvii and xxiv are single bonds; and wherein whenxvii is a double bond, xv, xiii and xx are single bonds.

In a particular embodiment of the compound of Formula VI, wherein R¹⁵,R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰, R²¹, and R²² are trivalent hydrocarbonscomprising 1 carbon atom; ii, iv, vi, viii, x, xiv, xvii, xviii, xxii,and xxiv are double bonds, and i, iii, v, vii, xi, xii, xiii, ix, xv,xvi, xix, xxi, xxiii, and xx are single bonds; the creep control agentis perylene-3,4,9,10-tetracarboxylic acid dianhydride, a compound havingthe chemical structure:

IV. Methods of Making Polyester Composition and Containers

As described above, the polyester compositions provided herein areuseful for making containers in which enhanced gas barrier propertiesare desirable. In short, such containers are made by forming the abovedescribed polyester compositions into the desired container byconventional methods such as melt forming. Suitable melt formingprocesses include, but are not limited to, injection molding, extrusion,thermal forming and compression molding of preforms followed by the blowmolding of the melt formed preforms into bottles. The particularlypreferred method for making the containers of this invention is stretchblow molding.

Methods for incorporating the gas barrier enhancing additive into thecontainer and polyester composition also are provided herein. Suchmethods also are well known to those skilled in the art. For example, anadditive can be fed directly into the polyester during the injectionmolding process, preblended with the polyester resin prior to injectionmolding, or incorporated at high concentrations with PET as masterbatchand then blended with the polyester resin prior to both injectionmolding of the preform and stretch blow molding of the container. Thoseskilled in the art will appreciate that such methods may be modifieddepending on the form of the additive being used. For example, whenusing additives in powder form, the polyester resin may be ground toreduce the size of the pellets and facilitate the formation of ahomogeneous blend.

FIG. 1 illustrates a system 10 in accordance with an embodiment of thisinvention for making a rigid container preform 12 (illustrated in FIG.2) and a rigid container 14 (illustrated in FIG. 3) from the preform. Asis shown in FIG. 1, PET 20 and a gas barrier enhancing additive 22 areadded to a feeder or hopper 24 that delivers the components to a hotmelt extruder 26 in which the components are melted and blended with apolyester. The hot melt extruder 26 then extrudes the molten mixture ofthe polyester 20 and gas barrier enhancing additive 22 into an injectionmolding device 28 to form the preform 12. The preform 12 is cooled andremoved from the injection molding device 28 and delivered to a stretchblow molding device 30 which stretch blow molds the preform 12 into afinished rigid container 14.

The melt residence time of the preform production is preferably lessthan five minutes and more preferably from about one to about threeminutes. The melt temperatures are desirably from about 260 to about300° C. and more desirably from about 270 to about 290° C. The meltresidence time begins when the PET 20 and gas barrier enhancing additive22 enter the melt extruder 26 and start melting, and ends afterinjection of the molten blend into the injection mold to form thepreform 12

V. Containers

As is well known to those skilled in the art, containers can be made byblow molding a container preform. Examples of suitable preform andcontainer structures are disclosed in U.S. Pat. No. 5,888,598, thedisclosure of which as it relates to the preform and containerstructures being expressly incorporated herein by reference.

A polyester container preform 12 is illustrated in FIG. 2. This preform12 is made by injection molding or compression molding PET based resinand comprises a threaded neck finish 112 which terminates at its lowerend in a capping flange 114. Below the capping flange 114, there is agenerally cylindrical section 116 which terminates in a section 118 ofgradually increasing external diameter so as to provide for anincreasing wall thickness. Below the section 118 there is an elongatedbody section 120.

The preform 12 illustrated in FIG. 2 can be stretch blow molded to forma container 14 illustrated in FIGS. 3 and 4. The container 14 comprisesa shell 124 comprising a threaded neck finish 126 defining a mouth 128,a capping flange 130 below the threaded neck finish, a tapered section132 extending from the capping flange, a body section 134 extendingbelow the tapered section, and a base 136 at the bottom of thecontainer. The container 14 is suitably used to make a packaged beverage138, as illustrated in FIG. 4. The packaged beverage 138 includes abeverage such as a carbonated soda beverage disposed in the container 14and a closure 140 sealing the mouth 128 of the container.

The polyester container optionally may comprise a plurality of layers.Those skilled in the art will appreciate that the polyester compositioncomprising the polyester and gas barrier additive may be disposed in anyof the one or more layers of such multilayer containers. For example,the polyester composition comprising the polyester and gas barrierenhancing additive may be disposed between two or more outer layers.

The preform 12, container 14, and packaged beverage 138 are but examplesof applications using the preforms of the present disclosure. It shouldbe understood that the process and apparatus provided herein can be usedto make preforms and containers having a variety of configurations.

The present disclosure is further illustrated by the following examples,which are not to be construed in any way as imposing limitations uponthe scope thereof. On the contrary, it is to be clearly understood thatresort may be had to various other embodiments, modifications, andequivalents thereof which, after reading the description therein, maysuggestion themselves to those skilled in the art without departing fromthe spirit of the present invention and/or the scope of the appendedclaims.

EXAMPLES Example 1

A bis(2-(benzoyloxy)ethyl) terephthalate) (hereinafter “BPO-1”) andbis(2-(benzoyloxy)ethyl)′-ethane-1,2-diyl diisophthalate (hereinafter“BPO-2”) were prepared by reacting bis(hydroxyethyl)terephthalate (BHET)with benzoic anhydride.

BPO-1 Preparation

Dry toluene (1000 mL) was added to a dry 200 mL three neck round bottomflask fitted with a mechanical stirrer, water cooled condenser cappedwith a desicant drying tube, and a pressure equalizing addition funnel.BHET (105.40 g, 0.415 moles) was added to the toluene with agitation,followed by triethylamine (126.7 mL, 0.913 mol). The toluene reactionmixture was heated to 50° C. and benzoyl chloride (128.33 g) was addeddrop wise at a rate sufficient to keep the reaction temperature at 90°C. The reaction mixture was maintained at 90° C. with agitation untilthe disappearance of the starting material was evident by thin layerchromatography. The reaction mixture was cooled to 40° C. and filteredto remove the precipitated triethylamine hydrochloride. The filtrate waswashed with an equal volume of 10% sodium hydroxide solution followed bywashing with water until a neutral pH was measured in the wash water.The toluene was dried with a desiccant and the solvent removed byevaporation. The remaining solid was purified by fractionalrecrystallization from chloroform using methanol.

Not wishing to be bound by any theory, it is believed that the reactionmechanism to produce the BPO-1 proceeds as follows:

BPO-2 Preparation

The BHET (101.47 g, 0.399 mol) was stirred and heated to 140-160° C.under mild vacuum conditions (20-25 torr) until a rapid release ofethylene glycol was achieved. The resulting PET oligomers were dissolvedin p-toluene sulfonic acid (100 mg) and a titanium catalyst Ti(OBu)₄(100 mg in 50 mL toluene, 13 ppm metal equivalent) was added (200 mLtotal volume added). Benzoic anhydride (76.1 g) was added slowly,resulting in formation of a biphasic system. A Dean-Stark trap wasattached and the mixture was refluxed until a sufficient amount of water(˜3 mL) was removed. The rate of water removal was significantly fasterthan for the BPO-1 preparation (in less than 24 hours the water removalwas sufficient); however, the reaction was allowed to proceed for 48hours in order to assure complete reaction. The reaction mixture wasthen cooled and filtered under vacuum to remove solids. The solids werewashed with acetone and then hexanes or ether and dried under vacuum.

Not wishing to be bound by any theory, it is believed that the reactionmechanism to produce the BPO-2 proceeds as follows:

Analysis of Solids

The solids from both of the foregoing reactions were analyzed using IRto identify the presence of two difference C═O stretches and thepresence of hydroxyl end groups. Additional characterization by acidnumber, hydroxyl end group determination, and GPC also were conducted.

Example 2

The relative volatility of these compounds was compared to previouslydescribed low molecular weight gas barrier additives. A known mass ofthe additive was heated in a 245° C. oven for a brief period of time,cooled, and the remaining mass evaluated. The following table comparesthe resulting rate of loss of the gas barrier additives.

TABLE 1 Comparison of Additive Volatility Rate of Mass Loss Additive (%per hour) Relative Rate Caffeine 137 1 BPO-2 1.02 0.00744 BPO-1 2.410.0179 0.11* 0.000803* *This data reflects the plateau region the BPO-1showed after the initial mass loss.

Although there were several possible sources of error (e.g., from therepeated heating and cooling, from the slow additional polymerization ofthe samples at these high temperatures after prolonged periods of time,and from the initial rapid mass loss due to the possible presence ofretained volatiles from the synthesis and purification of the additive),the data illustrates the significantly reduced rate of volatility ascompared to previously described low molecular weight additives. Thisreduced volatility indicates that the proposed gas barrier additivesshould pose no significant risk of plate-out or tool fouling during theinjection molding process.

Example 3

Additional experiments were conducted to evaluate potential syntheticroutes for the commercial production of BPO-1. Methods for commercialproduction of BPO-1 may desirably eliminate or significantly reduce thesolvent usage while maximizing product yield and quality.

A. BPO-1 Preparation from BHET and Methyl Benzoate

One method for preparing BPO-1 involved the direct esterification ofBHET (12.70 g, 0.0499 mol) with methyl benzoate (14.96 g, 0.110 mol)using the catalyst TYZOR® TNBT (E. I. du Pont de Nemours and Company,Delaware, United States) (0.3 g, 8.82*10⁻⁴ mol) and heated to 120° C.The melt temperature was then increased to 170° C. and the reaction wasallowed to proceed for 6 hours. The methanol produced in the reactionwas distilled off and a white precipitate was separated via filtrationand analyzed using thin-layer chromatography (TLC). The TLC analysisshowed the formation of BPO-1 (16.32 g, 70% conversion) in the presenceof a monoester and unreacted BHET.

Those of skill in the art should appreciate that other catalysts alsomay be used in the esterification of BHET. For example, zirconium,hathium, titanium catalysts (other than the one above), or the like, maybe employed as the catalyst in this process. Zirconium and hafniumcatalysts that may be used include ZrOCl₂*H₂O and HfCl₄*2THF,respectively. The optimum reaction conditions for the esterification mayvary depending on the catalyst used (e.g., mole ratios, catalyst levels,reaction times, and temperatures may be adjusted as needed). It shouldalso be noted that the term “esterification,” as used herein, refers toboth esterifications and processes commonly referred to as“trans-esterifications.”

In addition, other alkyl benzoates, including straight or branched alkylbenzoates, may also be used in the esterification. Benzoic acid may alsobe used instead of an alkyl benzoate. Not wishing to be bound by anytheory, it is believed that the esterification reaction produces waterwhen benzoic acid is used instead of an alkyl benzoate. The waterproduced by the reaction of benzoic acid may limit the effectiveness ofthe catalysts. The esterification may also be run in the presence of asuitable organic solvent. Non-limiting examples of suitable organicsolvents include benzene, toluene, or xylene.

B. BPO-1 Preparation from BHET and Methyl Benzoate and Recovery ViaVacuum Distillation

Another method for preparing BPO-1 involved the reaction of BHET (150.02g, 0.59 mol) with methyl benzoate (321.31 g, 2.36 mol) using thecatalyst TYZOR® TPT (E. I. du Pont de Nemours and Company, Delaware,United States) (0.24 g, 8.44*10⁻⁴ mol). The reaction vessel was purgedusing nitrogen and the mixture was gradually heated to 210° C. Thereaction proceeded until methanol evolution ceased (approximately 5hours from the start of heatup to completion or approximately 3 hours,50 minutes from the start of methanol evolution). The crude reactionproduct was transferred into another container and became a thick pasteof white precipitate in the excess methyl benzoate upon cooling.Analysis of the crude reaction product dissolved in chloroform andspotted on a TLC plate (stationary phase: neutral alumina) using amobile phase of chloroform showed complete conversion of the BHETstarting material to predominately BPO-1 (R_(f)˜0.84) with small amountsof oligomeric material (dimer—R_(f)˜0.75; trimer—R_(f)˜0.61). The excessmethyl benzoate starting material appeared at R_(f)˜0.92.

The BPO-1 was isolated from the crude reaction mixture by vacuumdistillation to remove the excess methyl benzoate. A vacuum of ˜250 mmHg was used and the vessel temperature was kept below 180° C. tominimize the risk of distilling the BPO-1 product. Those skilled in theart will appreciate that the temperatures and strength of the vacuum maybe adjusted by a person of skill to obtain similar results (e.g., ahigher vacuum may require a temperature well below 180° C.). Afterremoval of the excess methyl benzoate, the product was cooled andsolidified below 105° C. to give a faint yellow-white solid. Analysis ofthe product by TLC indicated that the product was predominately BPO-1with small amounts of oligomeric material present.

This reaction and separation was repeated while modifying severalvariables (e.g., temperature, catalyst weight percentage, catalyst, andmolar ratio of methyl benzoate to BHET). Each reaction was conductedusing 150 g (0.59 mol) of BHET. The weight percentages of the catalystsin the table are based on the total weight of the reactants. Thereaction conversion is based on the amount of evolved methanol relativeto the theoretical stoichiometric yield (37.81 g) of methanol from 150 gof BHET. The following table depicts the percent yield of methanol, thedegree of yellow color produced, and the presence of other oligomers ineach reaction.

TABLE 2 Comparison of BPO-1 Reaction Conditions Mole Temp Wt % Catalyst% Yield Yellow Oligomer Ratio (° C.) Cat. Type* MeOH Color** Present2.25 195 0.5 TPT 50.2 − − Yes 2.25 195 0.1 TPT 46.0 + + Yes 2.05 195 0.5TPT 56.5 − − Yes 2.05 195 0.1 TPT 34.9 + + Yes 2.15 195 0.3 TPT 50.2 −Yes 2.05 215 0.5 TPT 52.9 − − Yes 2.05 205 0.3 TPT 45.4 − Yes 2.05 2651.3 TPT 81.2 − − − − yes, very high 2.05 260 0.1 TPT 73.2 + + yes, veryhigh 4.00 210 1.0 TPT 90.0 − − − low, minor 2.50 210 1.0 TnBT 69.0 − − −Yes 3.00 210 1.0 TPT 81.2 − − − Yes 4.00 210 0.3 TPT 100.0 − low, minor4.00 210 0.1 TPT 100.0 + + low, minor 4.00 210 0.05 TPT 100.0 + + + +low, minor *TPT (tetra-isopropyl titanate), TnBT (tetra-n-butyltitanate) **Color grading scale: best color (+ + + +) to worst color (−− − −)

A number of catalysts may be employed in the esterification reaction, asdiscussed hereinabove. Not wishing to be bound by any particular theory,it is believed that minimizing the level of catalyst, such as thetitanate catalyst in the present example, may reduce the yellowing ofthe reaction mixture and/or products while maintaining good reactivity.In addition, the solubility of BPO-1 in methyl benzoate may be reducedwith the use of lower catalyst levels. This reduction in solubility mayaid the separation of the product from the excess methyl benzoate.

As previously stated, other alkyl benzoates, including straight orbranched alkyl benzoates, may be used successfully in theesterification. Typically, an excess of alkyl benzoate is used in theesterification reaction. Although a 2:1 molar ratio of alkyl benzoate toBHET is sufficient to form the diester, an excess of alkyl benzoate maybe used. In the present example, a 4:1 molar ratio of methyl benzoate isused. Any molar ratio of alkyl benzoate to BHET in excess of 2:1 may beused so long as the reaction conditions are adjusted to accommodate theselected excess of alkyl benzoate. An excess may not be inefficient froma manufacturing or economic perspective, because the excess, unreactedalkyl benzoate may be recovered and reused in subsequent processes.

Those skilled in the art should further appreciate that this process maybe scaled up for commercial production. FIG. 5 illustrates an overallprocess flow including the mass balance for the production of 100 lbs.of BPO-1. The depiction assumes quantitative yield and high efficiency.The raw material costs of the product may be reduced significantly dueto the recovery and recycling of methyl benzoate and sale of themethanol byproduct.

C. BPO-1 Preparation from BHET and Benzoic Anhydride

BHET (35.09 g, 0.138 mol) and benzoic anhydride (69.39 g, 0.276 mol)(90%purity, Sigma-Aldrich) were combined at a molar ratio of 2.0 benzoicanhydride to BHET. The vessel was purged with nitrogen and the mixtureslowly heated to 150° C. A light, yellow-colored, clear melt wasachieved at 105° C. As the temperature continued to rise, crystals ofbenzoic acid were observed condensing on the upper walls of the flaskand at the opening of the vertical column; however, no benzoic acidcrystallized into the column itself. Upon completion of the reaction, aheat gun was used to melt the benzoic acid crystals back into themixture.

The reaction mixture was sampled after 1 hour and 2 hours at 150° C. tomonitor progress via TLC (alumina, CHCl₃). After 1 hour, TLC indicatedthe presence of starting material, benzoic acid, the monobenzoate esterof BHET, BPO-1, and BPO-2. The BPO-1 spot was by far the largest anddarkest spot observed. After 2 hours, TLC indicated the completion ofreaction with the disappearance of the starting materials and themonobenzoate ester of BHET. The sample showed a large, dark BPO-1 spotwith a small, faint BPO-2 spot. The isolated crude product (102.99 g)solidified below 90° C. and was easily broken up and ground to a powderafter cooling to room temperature. Two different methods were then usedto remove the benzoic acid from the BPO-1: a saturated sodiumbicarbonate wash or a methanol wash.

For the sodium bicarbonate wash, the powdered crude product (20.014 g)was mixed with 100 mL of 1M NaHCO₃ solution. The slurry was then vacuumfiltered, washed with additional NaHCO₃ solution, subsequently washedwith distilled water, and allowed to dry in a vacuum oven. After drying,the solid weighed 12.201 g (60.96% of the original crude productsample). If all the crude product were treated in this manner, theestimated overall yield from the NaHCO₃ workup is >95%. TLC showed theNaHCO₃ treated product to be substantially BPO-1 with a smaller amountof BPO-2. The product had a melting point range of 85° C. to 100° C.according to a Fisher-Johns apparatus. The product retained some of itslight pink coloration (believed to be an impurity from the benzoicanhydride).

For the methanol wash, the powdered crude product (20.007 g) was mixedwith methanol (80.005 g). The slurry was vacuum filtered, washed withfresh methanol and placed in a vacuum oven to dry. After drying, thesolid weighed 11.264 g (56.30% of the original crude product sample). Ifall the crude product were treated in this manner, the estimated overallyield from the methanol workup is >90%. TLC showed the methanol treatedproduct to be primarily BPO-1 with a small amount of BPO-2. This productgave a Fisher-Johns melting point range of 90° C. to 105° C. Themethanol removed the light pink coloration from the product, and theproduct had a melting point range closer to that of pure BPO-1 (102° C.to 107° C.).

Not wishing to be bound by any particular theory, it is believed thatthe esterification of methyl benzoate with BHET leads to the formationof dimethyl terephthalate (DMT). DMT may form because of the reactionconditions required to instigate the esterification of methyl benzoatewith BHET. Although the desired product may be formed in the presence ofDMT, DMT may be formed in amounts sufficient to detrimentally affectyields of BPO-1. The formation of DMT, however, does not occur whenbenzoic anhydride is reacted with BHET.

In the present example, a molar ratio of benzoic anhydride to BHET of2.0 was used. Using an excess of benzoic anhydride may be efficient froman economic and manufacturing perspective, because any excess orunreacted benzoic acid may be recovered and sold or re-used in futureprocesses. FIG. 6 illustrates an overall process flow including massbalance for the production of 100 lbs. of BPO-1 assuming quantitativeyield and high efficiency. The raw material cost of the product shouldbe reduced after credits for the recovery or sale of benzoic acid arecalculated.

Example 4

Preparation of Preforms and Stretch Blow Molded Containers

A polyester composition was prepared by blending a ground 1103 PET resin(Invista, Spartanburg, S.C.) with either 3 or 4 wt % of the BPO-1 gasbarrier additive. The polyester composition was injection molded usingconventional methods to obtain a container preform. The containerpreforms appeared to be of good quality in terms of clarity and shapewithout any indication of buildup on the core pin or in the threadsplits and other parts of the injection molder, indicating there was nosubstantial plate-out on the injection molding equipment. The containerpreforms then were stretch blow molded using conventional methods toobtain bottles which were clear, colorless to the eye, andindistinguishable from one another.

The amount of the additive and intrinsic viscosity of the polyestercomposition, preform, and container are set forth in the table below.

TABLE 3 Polyester Resin and Preform Composition and I.V. BPO-1 I.V. (wt%) (dL/g) Resin 0 0.83 Preform 0 0.78 Preform 3 0.74 Preform 4 0.72

Those skilled in the art will appreciate that the observed decrease inI.V. with increasing amounts of gas barrier additive is not unusual andthat the I.V. could be increased by using a polyester resin having ahigher I.V.

Analysis of Container Thermal Stability

A thermal stability test was performed on the stretch blow moldedcontainers prepared hereinabove to measure physical changes in containerdimensions caused by temperature and pressure stresses. Twelve testcontainers prepared from the control (PET+no additive), 3 wt % additive(PET+3 wt % BPO-1), and 4 wt % additive (PET+4 wt % BPO-1) were tested.

The dimensions of the empty containers were measured and the containersthen were filled with carbonated water to 4.1+/− volumes and capped. Thefilled containers were exposed to ambient temperature overnight and thedimensions were measured to determine the percent change. Afterdimensional measurements are taken at ambient temperature, the sampleswere stored in an environmental chamber at 38° C. for 24 hours and thedimensions were measured again to determine the percent change. Theminimum, average, and standard deviation of all dimensions werecalculated for each day of testing. The average critical dimensionchanges are summarized in the table below.

TABLE 4 Summary of Average Container Thermal Stability Average % 3 wt %4 wt % Expansion Control BPO-1 BPO-2 Heel Diameter 0.10% 0.10% 0.05%Pinch Diameter 4.22% 3.90% 4.42% Pinch/Heel Ratio 4.13% 3.80% 4.38%Label Diameter 1.64% 1.98% 2.31% Height (Support 1.97% 2.05% 2.19% Ring)Analysis of Container Strength

The container strength of the stretch blow molded containers preparedhereinabove also was evaluated by assessing the peak load of thecontainers as well as the bottle burst pressure, expansion volume, andpercent expansion. Such tests are well known to those skilled in the artand are briefly described below. Twelve test containers prepared fromthe control (PET+no additive), 3 wt % additive (PET+3 wt % BPO-1), and 4wt % additive (PET+4 wt % BPO-1) were tested.

The peak load and peak deflection of the containers were measured with atensile/compression tester apparatus with non-vented steel load plates.The non-vented load plates were moved downward until the resistance toloading peaked and the containers lost column strength and deformed. Themaximum load and location of failure was recorded for each un-filledcontainer at 3.75 mm (0.150 inch) deflection. If the maximum load wasprior to 3.75 mm (0.150 in.) deflection, the maximum load and deflectionat which it occurred were recorded.

The burst pressure strength and the volumetric expansion of thecontainers were evaluated by first pressurizing the containers withwater as quickly as possible to a pressure of 9.18 bar (135 psi). Thepressure inside the containers was maintained for 13 seconds and thenincreased at a rate of 0.68 bar (10 psi) per second up to a maximum of20.4 bar (300 psi) or failure and the burst (or failure) pressure andvolumetric expansion of each container was recorded.

TABLE 5 Summary of Average Container Strength Average Container 3 wt % 4wt % Strength Control BPO-1 BPO-2 Peak Deflection (mm) 1.446 1.571 1.446Peak Load (g) 24686.761 24762.360 — Burst Pressure (psi) 268.0 253.0239.2 Expansion Volume (mL) 260.0 216.10 197.1 % Expansion 73.2 60.955.5

Despite the addition of the gas barrier additive to the polyester, thecontainer thermal stability and strength generally were notsignificantly diminished as often may be observed upon the addition ofprior art gas barrier additives.

Example 5

Containers were prepared as described in Example 4 hereinabove using theabove-described polyester, both alone and in combination with 3 wt % ofa gas barrier additive. The gas barrier additives included dibenzoylisosorbide (DBI), dicyclohexyl terephthalate (DCT), dicyclohexylnaphthalene-2,6-dicarboxylate (DCN), and bis(2-(benzoyloxy)ethyl)terephthalate (BPO-1).

Containers were filled with dry ice to achieve an internal pressure of56 psi. The loss rate of carbon dioxide from the bottles was measured at22° C. and 50% RH using the method described in U.S. Pat. No. 5,473,161,which is hereby incorporated by reference in its entirety. The barrierimprovement factor (BIF) was defined as the ratio of the carbon dioxideloss rate of the polyester container without additive divided by thecarbon dioxide loss rate of the polyester container with additive. Theshelf life of the simulated carbonated soft drink for each containeralso was calculated as described by U.S. Pat. No. 5,473,161. The resultsare summarized in the table below.

TABLE 6 Summary of Container Shelf Life and BIF 3 wt % 3 wt % 3 wt % 3wt % Control DBI DCT DCN BPO-1 Shelf Life 7.24 8.62 8.39 7.75 9.27(Weeks) BIF — 1.19 1.14 1.06 1.24

As the foregoing illustrates, the addition of the gas barrier additivesto the polyester significantly enhanced the shelf life and gas barrierproperties of containers as compared to the containers prepared frompolyester without the gas barrier additives. Surprisingly, the additionof just 3 wt % of BPO-1 increased the container BIF by nearly 25% (1.24)and the shelf life by two weeks.

Example 6

Containers also were prepared using the above-described polyester, bothalone and in combination with creep control agents as set forth in U.S.Pat. No. 8,110,265. 500 ppm or 1000 ppm of pyromellitic dianhydride(PMDA) were used as exemplary creep control agents. The average shelflife and barrier improvement factor of the containers were determined asdescribed in Example 5.

TABLE 7 Summary of Container Shelf Life and BIF 3 wt % 3 wt % PMDA PMDAPMDA (500 ppm) + PMDA (500 ppm) + Control DCN BPO-1 (500 ppm) (1000 ppm)DCN (3 wt %) BPO-1 (4 wt %) Shelf Life 7.24 7.75 9.27 9.46 9.01 7.6210.04 (Weeks) BIF — 1.06 1.24 1.13 1.19 1.09 1.39

Applicants surprisingly have discovered that the embodiments of theclaimed gas barrier additives not only enhance the container gas barrierproperties and shelf life, but also provide an additive effect whencombined with certain creep control agents. As the foregoingillustrates, the gas barrier additive (BPO-1) and creep control agent(PMDA) improved the container BIF by over 10% (1.24 to 1.39) and theshelf life by over half a week (9.46 to 10.04).

Example 7

Containers also were prepared using other polyester resins incombination with gas barrier enhancing additives and/or creep controlagents. The other polyester resins included 1103 A (Invista,Spartanburg, S.C.) and MMP 804 (PET Processors L.L.C., Painesville,Ohio).

A CO₂ permeation test was used to determine the shelf life of thecontainers. The bottles were filled with carbonated water at 4.2 v/v andthe loss rate of loss rate of carbon dioxide from the bottles wasmeasured at 22° C. and 50% RH using QuantiPerm. The permeation rates(mL/pkg/day) were used to calculate the percentage loss of carbonationper week and shelf life. The sorption also was estimated by theQuantiPerm software and the percentage of volume expansion was measuredfor each container.

TABLE 8 Summary of Container Shelf Life Polyester % Ex- % CO₂ SorptionShelf life Composition pansion loss/week % (weeks) BIF 1103 A Resin 6.262.54 1.59 6.31 — 1103 A Resin + 4.86 2.24 1.63 7.79 1.13 500 ppm PMDA1103 A Resin + 7.42 2.20 1.57 6.72 1.15 500 ppm PMDA + 4% BPO-1 MMP 804Resin 4.36 2.53 1.98 6.97 — MMP 804 Resin + 5.11 1.92 1.96 8.78 1.32 3%DBI MMP 804 Resin + 4.64 1.88 1.97 9.21 1.35 3% DBI + 500 ppm PMDA

As can be seen from the foregoing, the addition of the gas barrieradditive and creep control agent significantly increased the shelf lifeof containers prepared from different types of polyester resins.

Example 8

The mechanical properties of the containers of Examples 5 and 6 alsowere evaluated by measuring the creep of the containers. The averagepercent bottle creep is displayed in Table 9 and illustrated in FIG. 7.

TABLE 9 Summary of Container Creep Over 8 Weeks Averaged % Bottle CreepAfter 1 2 3 4 5 6 7 8 Variable Fill Wk. Wks. Wks. Wks. Wks. Wks. Wks.Wks. Control 3.78 5.58 5.35 5.23 5.42 5.29 5.24 5.43 3 wt % DBI 3.475.64 5.64 4.93 5.42 5.31 5.26 5.19 5.45 3 wt % DCT 3.36 5.31 5.89 5.065.37 5.19 5.36 5.22 5.11 3 wt % DCN 3.47 5.24 5.13 5.26 5.37 5.27 5.075.28 5.09 3 wt % BPO-1 3.35 4.99 5.07 4.80 4.80 5.27 5.04 4.86 4.71 PMDA(500 ppm) 2.81 4.20 4.37 4.37 4.23 4.17 4.16 4.40 4.46 PMDA (1000 ppm)3.14 4.61 4.65 4.76 4.72 4.57 4.68 4.83 4.85 PMDA (500 ppm) + 3.44 5.855.68 5.64 6.05 5.43 5.56 5.45 5.48 DCN (3 wt %) PMDA (500 ppm) + 3.675.56 5.82 5.53 5.48 5.51 5.94 5.60 5.99 BPO-1 (4 wt %)

As can be seen from the foregoing, the addition of the gas barrieradditive did not significantly increase the creep of the containers.Surprisingly, the gas barrier additive BPO-1 showed a reduced averagepercent bottle creep over the entire 8 week period as compared to thecontainer made from a polyester with no additives, indicating that thegas barrier additive did not significantly impair the container'smechanical properties.

Example 9

The aesthetics of the containers from Examples 5 and 6 also wereevaluated by measuring the color and clarity of the containers. Thecolors of the containers were measured with a Hunter lab colorimeter.The results are shown in Table 10. Hunter L*,a*,b* color space is a3-dimensional rectangular color space based on the opponent-colorstheory and expanded in the yellow region, wherein on the L* (lightness)axis white is 100 and black is 0, wherein on the a* (red-green) axis redis positive, green is negative, and neutral is 0; and wherein on the b*(blue-yellow) axis yellow is positive, blue is negative, and neutral is0. DE* is a measure of the total color difference, calculated by takingthe square root of the sum of the squares of the changes in L*,a*,b*.The data in Table 10 represent the average of 9 measurements.

TABLE 10 Analysis of Container Haze L* a* b* Haze dE*ab Variable (D65)(D65) (D65) (D1003-95)(C) (D65) Control 94.85 −0.046 0.821 1.236 0.096 3wt % DBI 94.91 −0.040 0.830 1.161 0.111 3 wt % DCT 94.73 −0.016 0.6502.308 0.207 3 wt % DCN 94.95 0.016 0.687 1.489 0.226 3 wt % BPO-1 94.86−0.032 0.688 1.232 0.169 PMDA 94.87 −0.043 0.787 1.227 0.088 (500 ppm)PMDA 94.69 −0.014 1.017 1.448 0.329 (1000 ppm) PMDA 94.83 0.016 0.6561.688 0.200 (500 ppm) + DCN (3 wt %) PMDA 94.79 −0.037 0.771 1.252 0.089(500 ppm) + BPO-1 (4 wt %)

As can be seen from the foregoing, the use of the proposed gas barrieradditives generally does not significantly impair the aestheticappearance of the containers. In particular, the combination of the gasbarrier additive (BPO-1) and creep control agent (PMDA) surprisingly hada insubstantial color difference as compared to the container made fromthe polyester without additives.

Example 10

Preparation of Preforms and Stretch Blow Molded Containers containingPEM

A polyester composition was prepared by blending a ground 1103 Apolyester resin (Invista, Spartanburg, S.C.) with either 3 or 4 wt % ofPEM, a gas barrier additive having the chemical formula:

The polyester composition was injection molded using conventionalmethods to obtain a container preform. The container preforms appearedto be of good quality in terms of clarity and shape without anyindication of buildup on the core pin or in the thread splits and otherparts of the injection molder, indicating there was no substantialplate-out on the injection molding equipment. The container preformsthen were stretch blow molded using conventional methods to obtainbottles which were clear, colorless to the eye, and indistinguishablefrom one another.

The amount of the additive and intrinsic viscosity (I.V.) of thepolyester composition, preform, and container are set forth in the tablebelow.

TABLE 11 Polyester Composition and Preform I.V. Polyester IntrinsicViscosity Composition (I.V.) (dL/g) 1103 A Resin 0.83 1103 A Preform0.80 1103 A Resin + 3% 0.79 PEM-1 Preform 1103 A Resin + 4% 0.79 PEM-1Preform 1103 A Resin + 4% 0.84 PEM-1 + 750 ppm PMDA

As the foregoing illustrates, an acceptable I.V. loss of 0.03 dL/g wasachieved during the conversion of the resins into preforms. Nosignificant difference in I.V. was observed between the 1103 A controlpreforms and the preforms molded with 3% and 4% PEM-1. The I.V. of thepreforms produced with PMDA at 750 ppm and PEM-1 at 4% was considerablyhigher than those molded without PMDA.

Those skilled in the art will appreciate that the observed decrease inI.V. with increasing amounts of gas barrier additive is not unusual andthat the I.V. could be increased by using a polyester resin having ahigher I.V.

Example 11

Containers were prepared using conventional methods using the polyestercompositions in Example 10 and evaluated using the methods described inExample 7. The results are summarized in the table below.

TABLE 12 Shelf life and Barrier Improvement Factor (BIF) ResultsPolyester % Ex- CO2 % Sorption Shelf life Composition pansion loss/week% (wks.) BIF Control 3.72 1.881 1.99 10.7 1.00 3% PEM-1 3.79 1.623 1.9912.2 1.18 4% PEM-1 3.78 1.597 1.99 12.4 1.17 4% PEM-1 & 3.92 1.523 1.9912.9 1.25 750 ppm PMDA

As the foregoing illustrates, the addition of the gas barrier additivesto the polyester significantly enhanced the shelf life and gas barrierproperties of containers as compared to the containers prepared frompolyester without the gas barrier additives. Surprisingly, the additionof just 3 wt % of PEM-1 increased the container BIF by nearly 20% (1.18)and the shelf life by approximately two weeks.

It should be apparent that the foregoing relates only to the preferredembodiments of the present disclosure and that numerous changes andmodification may be made herein without departing from the spirit andscope of the invention as defined by the following claims andequivalents thereof.

We claim:
 1. A method for enhancing the mechanical properties of apolyester container, the method comprising: blending a polyester with atleast one gas barrier additive to form a polyester composition having anI.V. from about 0.65 dL/g to about 1.0 dL/g; and stretch blow moldingthe polyester composition into a polyester container; wherein the atleast one gas barrier additive comprises a compound having the chemicalstructure of Formula I:

wherein X and X⁶, independent of one another, comprise hydrogen, halide,heteroatom, amino, amido, alkylamino, arylamino, alkoxy, aryloxy, nitro,acyl, cyano, sulfo, sulfato, mercapto, imino, sulfonyl, sulfenyl,sulfinyl, sulfamoyl, phosphonyl, phosphinyl, phosphoryl, phosphino,thioester, thioether, anhydride, oximno, hydrazino, carbamyl, phosphonicacid, phosphonato, or a C₁-C₁₀ monovalent hydrocarbon which isunsubstituted or substituted with one or more functional moieties;wherein X¹, X², X³, X⁴, and X⁵, independent of one another, comprise aheteroatom or a C₁-C₁₀ divalent hydrocarbon, wherein each heteroatom orC₁-C₁₀ divalent hydrocarbon is unsubstituted or substituted with one ormore functional moieties or one or more C₁-C₁₀ hydrocarbyls that areunsubstituted or substituted with one or more functional moieties;wherein s, t, u, and v, independent of one another, is a number from 0to 10; and wherein when X³ comprises a C₆ or C₁₀ divalent aromatichydrocarbon, X and X⁶, independent of one another, comprise a hydrogen,halide, heteroatom, hydroxyl, amino, amido, alkylamino, arylamino,alkoxy, aryloxy, nitro, acyl, cyano, sulfo, sulfato, mercapto, imino,sulfonyl, sulfenyl, sulfinyl, sulfamoyl, phosphonyl, phosphinyl,phosphoryl, phosphino, thioester, thioether, anhydride, oximno,hydrazino, carbamyl, phosphonic acid, phosphonato, or a C₃-C₁₀monovalent cyclic or heterocyclic non-aryl hydrocarbon that areunsubstituted or substituted with one or more functional moieties. 2.The method according to claim 1, wherein the gas barrier additivecomprises a compound having the chemical structure of Formula I, whereinX and X⁶ each comprise a phenyl group, a naphthyl group, or a cyclohexylgroup.
 3. The method according to claim 1, wherein the gas barrieradditive comprises a compound having one of the following chemicalstructures according to Formula I:


4. The method according to claim 1, wherein the gas barrier additive ispresent in the polyester composition in an amount in the range of about0.1 to about 10 weight percent of the polyester composition.
 5. Themethod according to claim 1, wherein the polyester comprisespolyethylene terephthalate.
 6. The method according to claim 1, whereinthe polyester composition comprises a poly(ethylene terephthalate) basedcopolymer having less than 20 percent diacid, less than 10 percentglycol modification, or both, based on 100 mole percent diacid componentand 100 mole percent diol component.
 7. The method according to claim 1,wherein the polyester composition comprises a polyester made using atleast one first polycondensation catalyst selected from the groupconsisting of metals in groups 3, 4, 13, and 14 of the Periodic Tableand comprising a catalyst residue remaining in the polyester fromformation of the polyester, the catalyst residue comprising at least aportion of the at least one first polycondensation catalyst.
 8. Themethod according to claim 1, wherein the gas barrier additive comprisesa compound having the chemical structure of Formula I, wherein X and X⁶,independent of one another, comprise a methyl, ethyl, phenyl, naphthyl,benzoate, hydroxyl, amino, amido, alkylamino, arylamino, alkoxy,aryloxy, or a monovalent C₃-C₅ aliphatic cyclic group; wherein X¹, X²,X⁴, and X⁵, independent of one another, comprise a divalent benzoate orC₁-C₂ aliphatic group; wherein s and v, independent of one another, is anumber from 0 to 2; wherein t and u, independent of one another, is anumber from 1 to 2; and wherein X³ comprises a divalent methyl, ethyl,phenyl, naphthyl, anthracenyl, a C₃-C₅ aliphatic cyclic group, a C₃-C₅cyclic group with one or more heteroatoms, or a C₆ bi-furan.
 9. Themethod according to claim 1, further comprising a creep control agent,wherein the creep control agent comprises a compound having the chemicalstructure:

wherein R¹, R², R³, and R⁴, independent of one another, may comprise aheteroatom, a tetravalent carbon atom, or a C₁-C₃ divalent or trivalenthydrocarbon; wherein each heteroatom, tetravalent carbon atom, or C₁-C₃divalent or trivalent hydrocarbon may be unsubstituted or substitutedwith one or more functional moieties or one or more C₁-C₁₀ hydrocarbylsthat may be unsubstituted or substituted with one or more functionalmoieties; wherein i, ii, iii, iv, v, and vi, independent of one another,comprise a single, double, or triple bond; wherein when i is a doublebond, ii and vi are single bonds; wherein when ii is a double bond, iand iii are single bonds; wherein when iii is a double bond, ii and ivare single bonds; wherein when iv is a double bond iii and v are singlebonds; wherein when v is a double bond, iv and vi are single bonds;wherein when vi is a double bond, i and v are single bonds; wherein viimay be a single bond, double bond, or no bond at all connects R³ and R⁴;wherein m, n, o, and p, independent of one another, may be 0 or 1;wherein when m is 0, bonds ii and iii form a single continuous bond;wherein when n is 0, bonds vi and v form a single continuous bond;wherein when o is 0, R⁴ is bonded to R¹ by a single bond; and whereinwhen p is 0, R³ is bonded to R² by a single bond.
 10. The methodaccording to claim 1, further comprising a creep control agent, whereinthe creep control agent comprises a compound having the chemicalstructure:

wherein A¹, A², R⁸, R⁹, and R¹⁰, independent of one another, maycomprise a heteroatom, a tetravalent carbon atom, a C₁-C₁₀ divalent ortrivalent hydrocarbon, or a C₁-C₁₀ hydrocarbyl that may be unsubstitutedor substituted with one or more functional moieties; wherein eachheteroatom, tetravalent carbon atom, or C₁-C₁₀ divalent or trivalenthydrocarbon may be unsubstituted or substituted with one or morefunctional moieties or one or more C₁-C₁₀ hydrocarbyls that may beunsubstituted or substituted with one or more functional moieties;wherein m′, n′, and p′, independent of one another, may be 0 or 1;wherein i, ii, and iii, independent of one another may be a single bondor a double bond; wherein t, u, v, and w, independent of one another maybe a single bond, double bond, or triple bond; and wherein q, r, and smay be from 0 to 10,000.
 11. The method according to claim 1, furthercomprising a creep control agent, wherein the creep control agentcomprises a compound having one of the following chemical structures:


12. The method according to claim 1, further comprising a creep controlagent, wherein the gas barrier additive comprises a compound having thechemical structure of Formula I, wherein X and X⁶, independent of oneanother, comprise a methyl, ethyl, phenyl, naphthyl, benzoate, hydroxyl,amino, amido, alkylamino, arylamino, alkoxy, aryloxy, or a monovalentC₃-C₅ aliphatic cyclic group; wherein X¹, X², X⁴, and X⁵, independent ofone another, comprise a divalent benzoate or C₁-C₂ aliphatic group;wherein s and v, independent of one another, is a number from 0 to 2;wherein t and u, independent of one another, is a number from 1 to 2;and wherein X³ comprises a divalent methyl, ethyl, phenyl, naphthyl,anthracenyl, a C₃-C₅ aliphatic cyclic group, a C₃-C₅ cyclic group withone or more heteroatoms, or a C₆ bi-furan.
 13. A method for enhancingthe mechanical properties of a polyester container, the methodcomprising: blending a polyester with at least one gas barrier additiveto form a polyester composition having an I.V. from about 0.65 dL/g toabout 1.0 dL/g; and stretch blow molding the polyester composition intoa polyester container having a Barrier Improvement Factor of at leastabout 1.05; wherein the at least one gas barrier additive comprises acompound having one of the following chemical structures:


14. The method according to claim 13, wherein the at least one gasbarrier additive comprises a compound having one of the followingchemical structures:


15. A method for enhancing the mechanical properties of a polyestercontainer, the method comprising: blending a polyester with at least onegas barrier additive to form a polyester composition having an I.V. fromabout 0.65 dL/g to about 1.0 dL/g; and stretch blow molding thepolyester composition into a polyester container; wherein the at leastone gas barrier additive comprises a compound having the chemicalstructure of Formula II:

wherein X and X⁶, independent of one another, comprise hydrogen, halide,heteroatom, amino, amido, alkylamino, arylamino, alkoxy, aryloxy, nitro,acyl, cyano, sulfo, sulfato, mercapto, imino, sulfonyl, sulfenyl,sulfinyl, sulfamoyl, phosphonyl, phosphinyl, phosphoryl, phosphino,thioester, thioether, anhydride, oximno, hydrazino, carbamyl, phosphonicacid, phosphonato, or a C₁-C₁₀ monovalent hydrocarbon which isunsubstituted or substituted with one or more functional moieties;wherein X¹, X², X³, X⁴, and X⁵, independent of one another, comprise aheteroatom or a C₁-C₁₀ divalent hydrocarbon, wherein each heteroatom orC₁-C₁₀ divalent hydrocarbon is unsubstituted or substituted with one ormore functional moieties or one or more C₁-C₁₀ hydrocarbyls that areunsubstituted or substituted with one or more functional moieties;wherein s and v, independent of one another, is a number from 1 to 10;wherein t and u, independent of one another, is a number from 0 to 10;and wherein when X³ comprises a C₆ or C₁₀ divalent aromatic hydrocarbon,X and X⁶, independent of one another, comprise a halide, heteroatom,amino, amido, alkylamino, arylamino, alkoxy, aryloxy, nitro, acyl,cyano, sulfo, sulfato, mercapto, imino, sulfonyl, sulfenyl, sulfinyl,sulfamoyl, phosphonyl, phosphinyl, phosphoryl, phosphino, thioester,thioether, anhydride, oximno, hydrazino, carbamyl, phosphonic acid,phosphonato, or a C₃-C₁₀ monovalent cyclic or heterocyclic non-arylhydrocarbon that are unsubstituted or substituted with one or morefunctional moieties.
 16. The method according to claim 15, wherein thegas barrier additive is present in the polyester composition in anamount in the range of about 0.1 to about 10 weight percent of thepolyester composition.
 17. The method according to claim 15, wherein thepolyester comprises polyethylene terephthalate.
 18. The method accordingto claim 15, wherein the polyester composition comprises a poly(ethyleneterephthalate) based copolymer having less than 20 percent diacid, lessthan 10 percent glycol modification, or both, based on 100 mole percentdiacid component and 100 mole percent diol component.
 19. The methodaccording to claim 15, further comprising a creep control agent, whereinthe gas barrier additive comprises a compound having the chemicalstructure of Formula II, wherein X and X⁶, independent of one another,comprise a methyl, ethyl, phenyl, naphthyl, benzoate, amino, amido,alkylamino, arylamino, alkoxy, aryloxy, or a monovalent C₃-C₅ aliphaticcyclic group; wherein X¹, X², X⁴, and X⁵, independent of one another,comprise a divalent benzoate or C₁-C₂ aliphatic group; wherein s and v,independent of one another, is a number from 1 to 2; wherein t and u,independent of one another, is a number from 1 to 2; and wherein X³comprises a divalent methyl, ethyl, phenyl, naphthyl, anthracenyl, aC₃-C₅ aliphatic cyclic group, a C₃-C₅ cyclic group with one or moreheteroatoms, or a C₆ bi-furan.
 20. The method according to claim 15,wherein the polyester composition comprises a polyester made using atleast one first polycondensation catalyst selected from the groupconsisting of metals in groups 3, 4, 13, and 14 of the Periodic Tableand comprising a catalyst residue remaining in the polyester fromformation of the polyester, the catalyst residue comprising at least aportion of the at least one first polycondensation catalyst.
 21. Themethod according to claim 15, wherein the gas barrier additive comprisesa compound having the chemical structure of Formula II, wherein X andX⁶, independent of one another, comprise a methyl, ethyl, phenyl,naphthyl, benzoate, amino, amido, alkylamino, arylamino, alkoxy,aryloxy, or a monovalent C₃-C₅ aliphatic cyclic group; wherein X¹, X²,X⁴, and X⁵, independent of one another, comprise a divalent benzoate orC₁-C₂ aliphatic group; wherein s and v, independent of one another, is anumber from 1 to 2; wherein t and u, independent of one another, is anumber from 1 to 2; and wherein X³ comprises a divalent methyl, ethyl,phenyl, naphthyl, anthracenyl, a C₃-C₅ aliphatic cyclic group, a C₃-C₅cyclic group with one or more heteroatoms, or a C₆ bi-furan.
 22. Themethod according to claim 15, wherein the step of blending a polyesterwith at least one gas barrier additive further comprises blending thepolyester with a creep control agent.
 23. The method according to claim15, wherein the gas barrier additive comprises a compound having thefollowing chemical structures according to Formula II:


24. The method according to claim 15, wherein the gas barrier additivecomprises a compound having one of the following chemical structuresaccording to Formula II:


25. The method according to claim 15, wherein the gas barrier additivecomprises a compound having the chemical structure of Formula II,wherein X and X⁶ each comprise a benzoate group.
 26. The methodaccording to claim 15, wherein the gas barrier additive comprises acompound having the chemical structure of Formula II, wherein X and X⁶each comprise a benzoate group and t and u are
 0. 27. The methodaccording to claim 15, wherein the gas barrier additive comprises acompound having the chemical structure of Formula II, wherein X and X⁶each comprise a benzoate group, t and u are 0, s and v are 1, and X¹ andX⁵ each comprise a divalent C₁ hydrocarbon.
 28. The method according toclaim 15, wherein the gas barrier additive comprises a compound havingthe chemical structure of Formula II, wherein X and X⁶ each comprise abenzoate group, s and v are 2, and X¹ and X⁵ each comprise a divalent C₁hydrocarbon.